Applications

Dow Caustic Soda Solution plays an important role in many industries, including.

Pulp and paper – The largest application for caustic soda worldwide. Uses include in pulping and bleaching processes, the de-inking of waste paper and water treatment.

Textiles – Used to process cotton and dye synthetic fibers, such as nylon and polyester.

Soap and detergents – Used in saponification, the chemical process that converts fat, tallow and vegetable oils into soap. It also is used to manufacture anionic surfactants, a crucial component in most detergents and cleaning products.

Bleach manufacturing – Used to make bleach, which has industrial and consumer applications such as mold and mildew control around the home.

Petroleum products – Used to explore, produce and process petroleum and natural gas.

Aluminum production – Used to dissolve bauxite ore, the raw material for aluminum production.

Caustic soda, as a 50% solution, is an odorless and colorless liquid. In all forms, caustic soda is highly corrosive and reactive. Caustic soda solution reacts readily with metals such as aluminum, magnesium, zinc, tin, chromium, bronze, brass, copper, and tantalum. Galvanized (zinc coated) materials should be avoided. Contact with acids, halogenated organics, organic nitro compounds, and glycol should be avoided. It reacts with most animal tissue, including leather, human skin, and eyes. It also reacts readily with various reducing sugars (i.e., fructose, galactose, maltose, dry whey solids) to produce carbon monoxide.

Upon cooling, the viscosity of the solution increases rapidly as the temperature falls below 18°C.

Stability and Storage Life

Caustic soda solution is a stable product but its storage life is dependent upon the storage conditions. If the caustic is exposed to air, a change in the product quality will be seen over time, since the caustic soda solution will pick up carbon dioxide to form sodium carbonate (NA2CO3) solids. In addition, iron pick up is common in carbon steel storage vessels or in lined carbon steel storage vessels where the liner has been damaged. Therefore, minimizing its exposure to air and its direct contact with iron containing metals will extend the storage life of caustic soda solution.

Over 95% of the capacity to produce chlorine and essentially 100% of the capacity to produce caustic soda (sodium hydroxide, NaOH) are based on the electrolysis of brine. In this process a sodium chloride (NaCl, salt) solution (brine) is electrolytically decomposed to elemental chlorine (in the anode compartment), and sodium hydroxide solution and elemental hydrogen (in the cathode compartment). A chemical facility which co-produces caustic soda and chlorine is typically referred to as a chlor-alkali (C/A) facility.

The overall reaction for the electrolytic production of caustic soda and chlorine is:

The electrolytic route to making caustic soda, by using sodium chloride as a raw material, is a co-product process, i.e., for each 1.1 kilogram of sodium hydroxide produced, one kilogram of chlorine is also produced. This ratio is referred to as an electrochemical unit (ECU).

Membrane Cell

Membrane cell technology is a relatively recent development. It differs from diaphragm cell technology in that the solutions surrounding each electrode are separated by a membrane rather than a diaphragm. The membrane is very selective and primarily allows the migration of sodium ions from the anode chamber to the cathode chamber. Saturated brine enters the anode compartment of the cell where chlorine gas is liberated. Since only sodium ions can pass through the membrane to the cathode (brine cannot pass through the membrane), the caustic soda (cell effluent) contains substantially less sodium chloride. No salt removal capabilities are required as in the diaphragm cell process.

Dow utilizes a fleet of tank trucks which are constructed of stainless steel or are lined to preserve product quality. Where weather conditions require, tank trucks are insulated.

Dow utilizes a fleet of insulated and lined tank cars equipped with suitable heating coils for caustic soda solution service. Tank cars are equipped to allow unloading from the top by air pressure or from the bottom by pump or air pressure and are lined to preserve product quality.

A fleet of contracted barges is used for deliveries to customers and terminals.

Marine vessels are also utilized to move large quantities from manufacturing facilities to terminals or overseas for export sales.

All vessels are inspected prior to loading to assure product quality and responsible transportation prior to shipment.

DOW Caustic Soda solution can be shipped in tank cars or tank trucks in the quantities shown in the tables below.

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